/*
 * Copyright 2002-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.core;

import java.io.IOException;
import java.io.InputStream;
import java.io.NotSerializableException;
import java.io.ObjectInputStream;
import java.io.ObjectStreamClass;

import org.springframework.lang.Nullable;
import org.springframework.util.ClassUtils;

/**
 * Special ObjectInputStream subclass that resolves class names
 * against a specific ClassLoader. Serves as base class for
 * {@link org.springframework.remoting.rmi.CodebaseAwareObjectInputStream}.
 *
 * @author Juergen Hoeller
 * @since 2.5.5
 */
public class ConfigurableObjectInputStream extends ObjectInputStream {

    @Nullable
    private final ClassLoader classLoader;

    private final boolean acceptProxyClasses;


    /**
     * Create a new ConfigurableObjectInputStream for the given InputStream and ClassLoader.
     *
     * @param in          the InputStream to read from
     * @param classLoader the ClassLoader to use for loading local classes
     * @see java.io.ObjectInputStream#ObjectInputStream(java.io.InputStream)
     */
    public ConfigurableObjectInputStream(InputStream in, @Nullable ClassLoader classLoader) throws IOException {
        this(in, classLoader, true);
    }

    /**
     * Create a new ConfigurableObjectInputStream for the given InputStream and ClassLoader.
     *
     * @param in                 the InputStream to read from
     * @param classLoader        the ClassLoader to use for loading local classes
     * @param acceptProxyClasses whether to accept deserialization of proxy classes
     *                           (may be deactivated as a security measure)
     * @see java.io.ObjectInputStream#ObjectInputStream(java.io.InputStream)
     */
    public ConfigurableObjectInputStream(
            InputStream in, @Nullable ClassLoader classLoader, boolean acceptProxyClasses) throws IOException {

        super(in);
        this.classLoader = classLoader;
        this.acceptProxyClasses = acceptProxyClasses;
    }


    @Override
    protected Class<?> resolveClass(ObjectStreamClass classDesc) throws IOException, ClassNotFoundException {
        try {
            if (this.classLoader != null) {
                // Use the specified ClassLoader to resolve local classes.
                return ClassUtils.forName(classDesc.getName(), this.classLoader);
            } else {
                // Use the default ClassLoader...
                return super.resolveClass(classDesc);
            }
        } catch (ClassNotFoundException ex) {
            return resolveFallbackIfPossible(classDesc.getName(), ex);
        }
    }

    @Override
    protected Class<?> resolveProxyClass(String[] interfaces) throws IOException, ClassNotFoundException {
        if (!this.acceptProxyClasses) {
            throw new NotSerializableException("Not allowed to accept serialized proxy classes");
        }
        if (this.classLoader != null) {
            // Use the specified ClassLoader to resolve local proxy classes.
            Class<?>[] resolvedInterfaces = new Class<?>[interfaces.length];
            for (int i = 0; i < interfaces.length; i++) {
                try {
                    resolvedInterfaces[i] = ClassUtils.forName(interfaces[i], this.classLoader);
                } catch (ClassNotFoundException ex) {
                    resolvedInterfaces[i] = resolveFallbackIfPossible(interfaces[i], ex);
                }
            }
            try {
                return ClassUtils.createCompositeInterface(resolvedInterfaces, this.classLoader);
            } catch (IllegalArgumentException ex) {
                throw new ClassNotFoundException(null, ex);
            }
        } else {
            // Use ObjectInputStream's default ClassLoader...
            try {
                return super.resolveProxyClass(interfaces);
            } catch (ClassNotFoundException ex) {
                Class<?>[] resolvedInterfaces = new Class<?>[interfaces.length];
                for (int i = 0; i < interfaces.length; i++) {
                    resolvedInterfaces[i] = resolveFallbackIfPossible(interfaces[i], ex);
                }
                return ClassUtils.createCompositeInterface(resolvedInterfaces, getFallbackClassLoader());
            }
        }
    }


    /**
     * Resolve the given class name against a fallback class loader.
     * <p>The default implementation simply rethrows the original exception,
     * since there is no fallback available.
     *
     * @param className the class name to resolve
     * @param ex        the original exception thrown when attempting to load the class
     * @return the newly resolved class (never {@code null})
     */
    protected Class<?> resolveFallbackIfPossible(String className, ClassNotFoundException ex)
            throws IOException, ClassNotFoundException {

        throw ex;
    }

    /**
     * Return the fallback ClassLoader to use when no ClassLoader was specified
     * and ObjectInputStream's own default class loader failed.
     * <p>The default implementation simply returns {@code null}, indicating
     * that no specific fallback is available.
     */
    @Nullable
    protected ClassLoader getFallbackClassLoader() throws IOException {
        return null;
    }

}
